This application claims the priority benefit of Japanese application serial no.2002-000878, filed on Jan. 7, 2002; 2002-326379, filed on Nov. 11, 2002.
1. Field of the Invention
This invention relates in general to an image forming device for forming images on a sheet, and a feed device.
2. Description of Related Art
In the application of image forming devices, such as a printer or a copier, improving the productivity of sequential image forming operations has been in demand. One method to meet the demand is to reduce the distance between respective sheets, which are transferred through an image forming section.
However, merely reducing the distance between sheets as they are separately fed from a sheet housing section, such as a sheet tray, is prone to pose a problem that a preceding sheet and a following sheet overlap each other in the image forming section. The problem occurs when a sheet slips upon its separate feeding, a sheet transfer speed changes as time passes or operational environment changes, or a stop time for registering is uneven.
To avoid such a problem, it has been practiced that at least the distance of several ten mm is provided between preceding and following sheets when images are formed sequentially on the sheets. As a result, however, a time span in which actually no image is formed becomes longer in the sequential image forming, deteriorating the productivity of image forming operation.
An image forming section employing an electrophotograhic method is constituted so as to operate without stopping even when the image forming section actually forming no image once it starts forming images. Therefore, a long distance between sequentially fed sheets results in a longer idling of the image forming section, reducing the life of the image forming section to produce less printed materials than the amount expected to be produced in the original lifetime.
It will be appreciated that the electrophotographic image forming section having a digital write-in means includes a polygon mirror constituting part of the write-in means, wherein the rotating speed of the polygon mirror is limited. It may be tried to increase the transfer speed of sheets in the image forming section, and addition to that, it is essential to correspondingly increase the rotating speed of the polygon mirror in order to improve the productivity of image forming operation. However, since the polygon mirror has a limit of its rotating speed, the above effort is limited.
Under these circumstances, the applicant of the present application disclosed in the Japanese Laid Open Publication No. He2001-130812 an image forming device, which can improve the productivity of image forming operation in the case of sequential image forming. In the image forming device, an inverting passage and a sheet inverting means are provided in the middle of a sheet transfer passage to make a sheet switch back, reducing the distance between the sheets sent to an image forming section.
According to the above image forming device having the inverting passage and the sheet inverting means, a sheet is transferred through the sheet transfer passage to be sent to the inverting passage, where the sheet is temporarily stopped and made to switch back, and is sent to the image forming section. Upon switching back, the speed of sending the sheet to the inverting passage, the speed of sending the sheet out of the inverting passage, and the timing of sending the sheet out of the inverting passage are controlled. As a result, the distance between the sheets, which are sent to the image forming section after having switched back, can be reduced, which improves the productivity of image forming operation.
In the operation of the image forming device described above, however, as a sheet is sent to the inverting passage at a high speed, the sheet may come to skew. Such a skewed sheet sent out of the inverting passage skews in the image forming section, rendering the corner of the sheet folded, thus causing a problem of what is called folded edge.
To handle such a problem, efforts have been made to correct the skew of a sheet just before it is sent out from the inverting passage. That is, it has been carried out a sidewise registration operation to set the sheet in a proper arrangement in the direction (horizontal direction) perpendicular to the sheet transfer direction so as to correct the skew of the sheet sent to the inverting passage.
According to conventional sidewise registration operations for sheet position adjustment, a pair of side fences or joggers are operated in a symmetrical manner so as to keep the center of a sheet in a constant position (what is called a center reference), or a sheet is set along a side guide so as to keep the edge of the sheet passing through the same position (what is called an edge reference). Therefore, when sheets having the same width are transferred, the passing position of the sheet edges are constantly the same, which makes it a common case without almost no exception that the sheet edges are adjusted by a sheet width commonly employed (for example, for adjusting the width of A4 size, or the length of A3 size withinxe2x80x94mm) and are passed between rollers.
When the sheet edges keep passing through the same position, however, the contact frequency between the sheet edges and the rubber rollers in a position other than the above same position becomes low, resulting in concentration of the contact between the edges and the rollers on the same position, damaging the part of the rollers corresponding to the position. This causes such an inconvenience as a surface exfoliation of a fixing roller, which leads to an earlier replacement of the roller. It will be also recognized that a temperature increase of the ends of the fixing rollers in the image forming section becomes another problem when the passing position of the sheet edges is constantly the same.
Besides, in conventional image forming devices, when a sheet on which images are formed is xe2x80x9csortedxe2x80x9d for every print job, it is common that an image-fixed sheet is sorted over by shifting the position of the sheet in the direction perpendicular to the transfer direction (doggy tail).
In such a case, however, a dedicated large finisher and the like is required, which makes impossible for a single image forming device to execute a sorting operation.
According to the foregoing description, it is an object of this invention to provide a image forming device and a feed device, with which concentrated contact of sheet edges with transfer means, such as rollers, in a prescribed position can be avoided, and earlier replacement of the rollers, such as fixing rollers in a image forming section, due to their surface exfoliation, can be prevented.
It is another object of this invention to provide an image forming device and a feed device, with which an operation of xe2x80x9csortingxe2x80x9d sheets according to the number of printing can be executed with a simple constitution.
According to an aspect of the present invention, in the image forming device of the present invention, sheets piled up and held in a sheet housing section are separately fed one after another by a separate feed means and an image is formed on the sheet transferred by a transfer means in an image forming section, comprises a movable member provided on the sheet transfer passage leading from said separate feed means to said image forming section and regulating the positioning of the edges of the sheet parallel to the transfer direction, the sheet being transferred through said sheet transfer passage; a regulating position change means for randomly changing a regulating position for positioning the sheet by said movable means; and a write-in position change means for changing a write-in start position in said image forming device in conformity to the position of the sheet transferred to said image forming section.
Accordingly, the regulating position for positioning the sheet by the movable member is randomly changed, and the write-in start position in the image forming section is also changed conforming to the changed regulating position for positioning the sheet, i.e., the position of the sheet which is to be transferred to the image forming section. As described above, the regulating position for positioning the sheet by the movable member is made changeable, so that concentration of the contact of sheet edges with transfer means, such as rollers, in a prescribed position is avoided and earlier replacement of rollers, such as fixing rollers in the image forming section, due to their surface exfoliation, can be prevented. Furthermore, a temperature increase of the ends of the fixing rollers in the image forming section can also be suppressed.
According to an aspect of the present invention, in the image forming device of the present invention, the regulation of positioning a sheet by said movable member is executed while the sheet on said sheet transfer passage is free from pressure application by any members.
Since positioning the sheet by the movable member is regulated while the sheet is free from any pressure application, the sheet comes to be temporarily free from any regulation of its position, which makes it possible to adjust smoothly the position of the sheet in the direction perpendicular to the proceeding direction.
According to an aspect of the present invention, in the image forming device of claim of the invention, the movable member has a pair of regulating members, which are arranged in parallel in the positions opposite to respective edges of a sheet parallel to the transfer direction, and said regulating position change means moves said each regulating member asymmetrically.
By moving asymmetrically the pair of regulating members arranged in parallel in the positions opposite to respective edges of the sheet parallel to the transfer direction, the position of the center line of each sheet can be shifted even if the size of the sheets are the same, so that the position regulation in the direction perpendicular to the proceeding direction can be easily made.
According to an aspect of the present of the invention, in the image forming device of the present invention, each regulating member is arranged in such a way that each can reciprocate independently in the direction of its contacting with or departing from the edge of a sheet parallel to the transfer direction.
Therefore, it becomes possible that the pair of regulating members each arranged in parallel in the positions opposite to respective sides of the sheet can be moved asymmetrically.
According to an aspect of the present invention, in the image forming device of the present invention, each regulating member is moved to the position where the distance between each regulating member becomes narrower than the width of a sheet.
Therefore, even if the widths of sheets are uneven (even if it is changed by an environmental factor), the position the sheet in its width direction can be adjusted without fail.
According to an aspect of the present invention, in the image forming device of the present invention, the movable member has one regulating member, which is arranged in the position opposite and parallel to the edges of a sheet parallel to the transfer direction, and a skewing roller arranged in a state that its axis is inclined against the direction of sheet width, wherein said regulation position change means moves said regulating member in the direction of its contacting with or departing from the sheet edges parallel to the transfer direction.
As the one regulating member, which is arranged in the position opposite and parallel to the edges of a sheet parallel to the transfer direction, is moved in the direction in which the member contacts with or departs from the sheet edges parallel to the transfer direction, the skewing roller shifts the sheet to the regulating member. This makes possible to shift the position of the center line of each sheet even if the size of the sheets are the same, so that the position regulation in the direction perpendicular to the proceeding direction can be easily made.
According to an aspect of the present invention, in the image forming device of the present invention, the skewing roller has a cutout formed into a flat surface on part of the outer periphery of the roller. Only when a part other than the cutout part is abutted on a sheet, the sheet sent to the transfer passage is transferred toward the regulation member.
Therefore, when the sheet is sent to the movable member, the cutout of the skewing roller is made to face the sheet and the skewing roller is rotated at the moment when the rear end of the sheet has passed through the transfer means. In this manner, the position of the sheet in the direction of its width can be easily adjusted. It will be appreciated that the constitution described above is simpler than the one for making or releasing contact with the sheet by swinging move of an arm and the like, free from impact noises produced upon catching the sheet, thus, advantageous for suppressing operational noise.
According to an aspect of the present invention, in the image forming device of the present invention, the regulation of positioning a sheet by said regulating means is sustained until the sheet is sent out of said sheet transfer passage.
When the sheet becomes free from the regulation by the regulating member, the sheet has already received pressure from the transfer means of the sheet transfer passage, so that the position change of the sheet in the following course of transfer can be prevented.
According to an aspect of the present invention, in the image forming device of the present invention, the regulating position change means changes the regulating position for positioning a sheet by said movable member so that the regulating position is shifted to the left and right in a prescribed distance per a prescribed number of printing.
Accordingly, it becomes possible to xe2x80x9csortxe2x80x9d the sheets by shifting the regulating position for positioning a sheet by said movable member to the left and right in a prescribed distance according to the number of printing, whereas xe2x80x9csortxe2x80x9d operation has been carried out conventionally by shaking the whole body of an ejecting unit via a large finisher. Thus, an image forming device can be miniaturized and a sort operation can be carried out with a simple constitution.
According to an aspect of the present invention, in the image forming device of the present invention, the regulating position change means changes sequentially or randomly the regulating position for positioning a sheet by said movable member by a prescribed width.
By changing the regulating position in such a manner, concentration of the contact of sheet edges with the transfer means, such as rollers, in a prescribed position is avoided and earlier replacement of the rollers, such as the fixing rollers in the image forming section, due to their surface exfoliation, can be prevented without fail.
According to an aspect of the present invention, the image forming device of claim 10 comprises a re-feed passage connected between the sheet ejecting side of said image forming section and said sheet passage; and a path shift member, which is arranged in a position where it interferes with only one regulating position for positioning a sheet by said movable member, the position of arrangement being on the sheet eject side of said image forming section, and which shifts the transfer direction of the sheet, on which an image is formed in said image forming section after the regulating position of said movable member has been changed, to said re-feed passage.
Accordingly, when the regulation position is changed by the movable member so that only the sheet which is to be transferred to the re-feed passage interferes with the path shift member, the transfer direction of the sheet with an image formed thereon by the image forming section can be easily shifted to the re-feed passage without shifting the position of the path sift member at a high speed, even in the case of interleaf feeding where the passage shift is made during a time span corresponding to a short distance between the sheets (frequent passage shift).
According to an aspect of the present invention, the image forming device of the present invention further comprises an inverting passage, which is connected to the sheet transfer passage leading from said separate feed means to said image forming section and to which a sheet transferred through the sheet transfer passage is temporarily sent; and a sheet inverting means, which can be shifted to a send-out state for making the sheet sent to said inverting passage switch back and sending it out to said transfer passage and shifted to an open state for allowing at least part of a proceeding sheet being sent out of said inverting passage and of a following sheet being sent to said inverting passage to overlap; wherein said movable member is provided on said inverting passage.
In the image forming device, a sheet is separately fed one after another by the separate feed means in the sheet housing section, transferred through the sheet transfer passage, and is sent to the inverting passage, where the sheet is temporarily stopped. Then, the sheet inverting means makes the sheet switch back, sending it out of the inverting passage to the image forming section, where an image is formed on the sheet.
Upon making the sheet switch back, the speed of sending the sheet to the inverting passage, the speed of sending the sheet out of the inverting passage, and the timing of sending the sheet out of the inverting passage are controlled, so that the distance between the sheets, which are sent to the image forming section after made to switch back, can be reduced. As a result, it becomes possible to keep the distance between the sheets small in a precise manner upon sending it to the image forming section, even if the feed timing of the sheet housing section comes to fluctuate or a transfer speed during the transfer to the inverting passage becomes uneven. Thus, the productivity of image forming operation in the image forming device can be improved.
Also, providing the movable member on the inverting passage makes it possible for the movable member to constantly carry out the regulation of positioning the sheet in a stable position.
According to an aspect of the present invention, in the image forming device, the sheet inverting means has a pair of rollers, one of which has a cutout formed on part of its outer periphery, wherein the direction of the cutout enables the shift between said send-out state for making the rollers nip a sheet and said open state for allowing the sheet to pass between both rollers.
The constitution described above is simpler than the one makes or releases contact with the sheet by swinging move of an arm and the like, free from impact noises produced upon catching the sheet, thus, operational noise can be suppressed.
According to an aspect of the present invention, in the image forming device, the outer periphery length, excepting the part of cutout, of one roller is made longer than the distance from the front end of a sheet in a state of just being released from contact with said rollers to the next said transfer means on said sheet transfer passage.
This arrangement enables the sure transfer of the sheet to the next transfer means.
According to an aspect of the present invention, in the image forming device, the sheet transfer passage leading from said separate feed means to said image forming section has an almost horizontal plane, via which a sheet is transferred in the direction almost horizontal to the surface of sheets stacked up and held in the sheet housing section and which is provided with said movable member.
The sheet separately fed one after another by the separate feed means is transferred to the almost horizontal plane, where the position of the sheet is adjusted randomly and the sheet is transferred in the direction almost horizontal to the surface of sheets stacked up and held in the sheet housing section, and is sent to the image forming section. In this manner, the sheet position can be adjusted randomly without inverting the transfer direction of the sheet (straight transfer).
According to an aspect of the present invention, in the image forming device, the sheet transfer passage leading from said separate feed means to said image forming section has an almost vertical plane, via which a sheet is transferred in the direction almost vertical to the surface of sheets stacked up and held in the sheet housing section and which is provided with said movable member. An elastic member is provided on said sheet transfer passage on the downstream side to said movable member in the transfer direction in order to hold the sheet by applying a low load to prevent it from falling off or moving because of its weight.
The sheet separately fed one after another by the separate feed means is transferred to the almost vertical plane, where the position of the sheet is adjusted randomly and the sheet is transferred in the direction almost vertical to the surface of sheets stacked up and held in the sheet housing section, then is sent to the image forming section. It will be appreciated that the elastic member can prevent the sheet from moving because of its won weight even when the sheet is released from pressure application by the transfer means during transfer. Therefore, the sheet position can be adjusted randomly without inverting the transfer direction of the sheet (straight transfer).
According to an aspect of the present invention, in the image forming device, the image forming section is an image forming section employing an electrophotographic method.
The image forming device forming images by the electrophotographic method can provide an operational effect equivalent to that described above.
According to an aspect of the present invention, in the image forming device, the image forming section is an electrophotograhic image forming section having a digital write-in means.
The image forming device forming images by the digital electrophotographic method can provide an operational effect equivalent to that described above.
According to an aspect of the present invention, a feed device separately feeds a sheet one after another by a separate feed means, said sheets stacked up and held in a sheet housing section, for an image forming device provided with an image forming section for forming an image on the sheet. The feed device comprises a movable member provided on a sheet transfer passage leading from said separate feed means to said image forming section and regulating the positioning of the edges of the sheet parallel to the transfer direction, the sheet being transferred through said sheet transfer passage; and a regulating position change means for randomly changing the regulating position for positioning the sheet by said movable means.
In the above image forming device, therefore, the regulating position for positioning the sheet by the movable member can be changed randomly. By making the regulation position for the sheet changeable, as mentioned above, concentration of the contact of sheet edges with transfer means, such as rollers, in a prescribed position is avoided and earlier replacement of rollers, such as fixing rollers in the image forming section, due to their surface exfoliation, can be prevented.
According to the image forming device of present invention, sheets piled up and held in a sheet housing section is separately fed one after another by a separate feed means and an image is formed on the sheet transferred by a transfer means in an image forming section, the image forming device comprises a movable member provided on the sheet transfer passage leading from said separate feed means to said image forming section and regulating the positioning of the sides of the sheet parallel to the transfer direction, the sheet being transferred through said sheet transfer passage; a regulating position change means for randomly changing a regulating position for positioning the sheet by said movable means; and a write-in position change means for changing a write-in start position in said image forming device in conformity to the position of the sheet transferred to said image forming section.
Accordingly, the regulating position for positioning the sheet by the movable member is randomly changed in the direction of sheet width, and the write-in start position in the image forming section is also changed conforming to the changed regulating position for positioning the sheet, i.e., the position of the sheet which is to be transferred to the image forming section. As described above, the regulating position for positioning the sheet by the movable member is made changeable in the sheet width direction, so that concentration of the contact of sheet edges with transfer means, such as rollers, in a prescribed position is avoided and earlier replacement of rollers, such as fixing rollers in the image forming section, due to their surface exfoliation, can be prevented. Furthermore, a temperature increase of the ends of the fixing rollers in the image forming section can also be suppressed.
In the image forming device of the present invention, the movable member has a pair of regulating members each arranged in the position opposite to respective sides of a sheet, wherein said regulating position change means moves said each regulating member asymmetrically.
By moving asymmetrically the pair of regulating members arranged in parallel in the positions opposite to respective sides of the sheet, the position of the center line of each sheet can be shifted even if the size of the sheets are the same, so that the position regulation in the direction perpendicular to the proceeding direction can be easily made.